No idea where you got that factoid from, but all Deoxys forms are 3rd Gen.
In Ruby and Sapphire it was Normal Form
In FireRed it was Attack Form
In LeafGreen it was Defence Form
In Emerald it was Speed Form
In Gen IV it could change between them.

Thank you! I did find this one but I wasn't sure if it was by the same artist. It does look similar but there are a few differences in the style that I was uncertain of. Do you think I should add it anyway?